Alzheimer's disease can spare local metacognition despite global anosognosia: Revisiting the confidence–accuracy relationship in episodic memory
Highlights
► Compared Alzheimer's participants and matched controls on metacognitive measures. ► At a local level, confidence judgments tracked recollection accuracy in both groups. ► At a global level, Alzheimer's participants underestimated their cognitive decline. ► Aspects of local and global metacognitive measures correlated across individuals. ► These metacognitive measures may tap distinct yet overlapping mental processes.
Introduction
It is well established that the early or mild stages of Alzheimer's disease (AD) impair basic cognitive abilities, but less is known about the effects of AD on metacognition. With respect to basic cognitive abilities, mild AD impairs the ability to consciously recall or recognize recently presented information (episodic memory), and also tends to impair the ability to flexibly control attention in cognitive tasks (executive functions). These are the most frequently studied aspects of cognition in early AD, and significant impairment in these basic cognitive abilities in older adults is the hallmark of AD (Storandt, 2008). In addition to these basic cognitive abilities, AD also can impair metacognition. Metacognition is knowledge about cognition (Flavell, 1979, Nelson and Narens, 1994), including the ability to think about one's own basic cognitive abilities (such as episodic memory or executive functions). It is important to understand how different aspects of metacognition might be affected by AD, because accurate insight into one's own cognitive decline is needed to realistically adjust one's personal goals and avoid risky behaviors (e.g., Starkstein, Jorge, Mizahi, Adrian, & Robinson, 2007).
The research literature on metacognition in AD can be broadly divided into two different areas of inquiry, depending on the scope of the metacognitive processes under consideration (for reviews, see Pannu and Kaszniak, 2005, Souchay, 2007). One research area is primarily concerned with an individual's awareness of their cognitive abilities and declines at a global level. By the global level, we mean general assessments or beliefs about cognitive abilities as they might apply to various activities of daily living (e.g., “In general, I believe my memory is failing me.”). Global metacognitive assessments are thought to involve long-term memory representations that contain information about one's personal abilities or self-efficacy beliefs (Mograbi, Brown, & Morris, 2009). In contrast to research on global metacognition, other research is primarily concerned with an individual's awareness of their cognitive abilities at a more local or task-specific level (Hertzog & Dunlosky, 2011). By local metacognition, we mean the online monitoring of cognitive task performance, as when people are asked to assess their performance across different experimental trials using subjective judgments such as confidence ratings (e.g., “I am not very confident in my recall of this particular item on this memory test.”). This distinction between global and local metacognition is based on the object of the metacognitive assessment (i.e., assessing one's general cognitive abilities versus one's task-specific cognitive abilities, respectively), but the memory representations that are used to make these different kinds of self-assessment might overlap. For example, global assessments of cognitive ability might be affected by recent experiences with cognitive tasks, and local assessments of task performance might be affected by general representations of self-efficacy.
Deficits in global metacognition are fairly well documented in AD. Many people with AD are thought to have some degree of anosognosia – a relative lack of awareness of the severity of their everyday cognitive declines – although the extent of awareness varies considerably across individuals (Kaszniak & Edmonds, 2010). Evidence for this kind of global metacognitive impairment has come from a variety of sources, including anecdotal reports, clinically structured interviews, and deviations between self-reports and informant-reports on questionnaires that probe everyday problems (Clare, 2004). This kind of metacognition has been investigated most extensively in the clinical research literature, because personal insight into overall cognitive impairments is likely to affect one's decisions and behaviors in a variety of real-life situations (e.g., avoiding risky driving, Cotrell & Wild, 1999).
The research literature is more mixed with respect to the possible effects of the early stages of AD on more local metacognitive abilities. Some cognitive tasks reveal impaired metacognition in AD relative to controls. For example, Schacter, McLachlan, Moscovitch, and Tulving (1986) found that AD participants overestimated their predicted recall abilities prior to a word recall task, and Souchay, Isingrini, and Gil (2002) found that AD impaired feeling-of-knowing judgments on a word recognition memory task. Moreover, some studies have found that individual variability in local metacognitive measures was related to more global metacognitive measures in AD, suggesting that these two kinds of metacognitive measures might tap overlapping processes or representations (Cosentino et al., 2007, Schmitter-Edgecombe and Seelye, 2011). In contrast to these studies, several other cognitive tasks demonstrate intact local metacognition in AD participants relative to controls. For example, Bäckman and Lipinska (1993) found that AD did not impair feeling-of-knowing judgments on a general knowledge task, and Moulin, Perfect and, Jones (2000) found that AD did not impair judgments-of-learning on a word recall task. AD participants also can accurately recalibrate their metacognitive ratings immediately after taking an episodic memory test (e.g., Schmitter-Edgecombe and Seelye, 2011, Stewart et al., 2010), suggesting relatively intact metacognitive performance once there is some degree of exposure to the task. These latter findings are inconsistent with the findings of impaired global metacognition in AD, and they suggest a discontinuity between local and global metacognitive measures.
There are several possible reasons for these discrepancies in the literature on local metacognition in AD, including the kinds of metacognitive judgments used and the aspects of cognition that were assessed by the task. Along these lines, Dodson, Spaniol, O'Connor, Deason, Ally, and Budson (2011) recently suggested that local metacognitive measures obtained during episodic memory tasks might be particularly sensitive to AD impairments, because episodic memory decline in the early stages of AD may make monitoring performance on these kinds of tasks particularly challenging (also see Pannu & Kaszniak, 2005). More specifically, Dodson et al. (2011) argued that AD participants have difficulty making accurate confidence judgments on a memory test due to increased susceptibility to false recollections that drive high-confidence errors. As described in the next section, however, relatively few studies have investigated the confidence–accuracy relationship in AD and the results have been mixed.
Section snippets
Episodic memory confidence
To our knowledge only three studies have investigated the effects of mild AD on the confidence–accuracy relationship in episodic memory retrieval (i.e., metamemory). The first two studies did not find impaired metamemory in AD. Pappas, Sunderland, Weingartner, Vitiello, Martinson, and Putnam (1992) found that AD participants and controls were equally accurate at using confidence judgments to assess their ability to recall the final word from studied sentences. A study by Moulin, James, Perfect,
The current study
The experiment reported here investigated the confidence–accuracy relationship in mild AD participants, using a relatively simple task that explicitly required recollection-based responding. This task has recently been used to identify metacognitive impairments in cognitively normal older adults (Wong, Cramer, & Gallo, in press). Participants studied objects presented as colored photos or as line drawings, and then took a picture recollection test followed by confidence judgments. This test
Participants
The memory task included 18 AD participants (mean age=76.2; SD=5.9; mean education=14.4 years, SD=2.4; 12 females) and 18 cognitively normal controls approximately matched on age, sex, and education (mean age=76.8 years; SD=7.4; mean education=15.4 years, SD=3.3, 13 females). AD participants were clinically diagnosed with probable AD based on NINCDS-ADRDA criteria (McKhann et al., 1984), and as expected, scores on the Mini Mental State Examination (Folstein, Folstein, & McHugh, 1975) were
Results
The results are presented in four sections. The first two sections present analyses of recollection accuracy obtained on the 2AFC judgments, and the overall distribution of confidence judgments. The third section reports the overall confidence assigned to correct and incorrect responses, as well as three summary measures of confidence judgment accuracy (Somers’ d, calibration error scores, and confidence discrimination). For each of these measures we compared the two original groups (n=18 per
Discussion
One of the primary findings from this study was that participants with mild AD were able to use confidence judgments to track the accuracy of their responses on a recollection test. Not only were our measures of metamemory significantly greater than chance in the AD group, but most of them did not differ significantly from those observed in a group of cognitively normal controls. These effects are consistent with the results of Pappas et al. (1992) and Moulin et al. (2003), and they extend
Acknowledgments
We are grateful to Barbara Eubeler, Gina Freed, James Mastrianni, and Raj Shah for assistance recruiting and characterizing AD participants. We also thank Chad Dodson for the calibration error measure. This work was supported by National Institute of Aging grants AG30345 and P30AG10161.
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